Recently, as the use of various smart devices and high-resolution large screens as well as televisions has increased, the types of display devices have been diversified. In particular, a variety of flat panel displays (FPDs) have been developed which can further reduce the weight and volume than a so-called cathode ray tube (CRT). Specifically, flat panel displays, such as liquid crystal displays (LCDs), thin film transistor-liquid crystal displays (TFT-LCDs), plasma display panels (PDPs), and electroluminescence devices have attracted attention.
The electroluminescence devices may be classified into an inorganic light emitting diode and an organic light emitting diode (OLED) according to a material of an emitting layer. The OLED is a self-luminous organic material that emits light by itself by using an electroluminescence phenomenon that light is emitted when a current flows through a fluorescent organic compound. The OLED can be driven at a low voltage and can be made light and thin. Additionally, since each device is a luminous type that emits light, light is adjusted by changing a current flowing through each device. Thus, a backlight is not required. An OLED display device implemented with such OLEDs has advantages such as a fast response time, high image quality, high luminescent efficiency, an ultra-thin structure, and a wide viewing angle.
Due to the above advantages, the prospect of the OLED display device is bright, and the demand for the OLED display device is increasing.
In the OLED display device, as each of elements emits light, the elements may be varied in use frequency and thus the lifespans of the elements may be varied.
Meanwhile, as a terminal such as a smartphone or a tablet PC is extensively spread, a display device has supported a screen mirroring function (for example, Miracast, or the like) of displaying, on a display unit, a mirroring image corresponding to a screen which is being displayed on a terminal. In general, the mirroring image may be fixedly displayed on a specific region (for example, a right upper end of the display unit) of the display unit. The mirroring image may have a higher frequency in including a still image, as compared with a broadcast image. Since an OLED element corresponding to a higher brightness region of the mirroring image continuously emits high-brightness light, the OLED element may have a lifespan reduced more rapidly than an OLED element provided in another region. When the lifespan of the element corresponding to the higher brightness region is rapidly reduced, the brightness of light emitted from the device may be relatively reduced.
Accordingly, the afterimage image is caused on a screen of an OLED display device due to the brightness difference from an element in another region and thus a user may feel inconvenient in viewing an image through the OLED display device, thereby serving as a main cause of degrading the reliability of a product.